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Title:Quantitative Photoacoustic Reaction-Rate Measurements Under Microcomputer Control
Author(s):Bross, Phillip Ralph
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Analytical
Abstract:Quantitative photoacoustic reaction-rate measurements under microcomputer control are demonstrated by the reaction of lysine and leucine with ninhydrin in a starch matrix. Coground amino acid/starch standards are analyzed in 200 seconds using initial reaction-rate conditions with a percent relative standard deviation generally better than 20% for 0.1 - 3.7 wt% standards. A single analysis requires approximately 10 mg of sample and 40 (mu)1 of ninhydrin reagent. The implications of this new photoacoustic application are the potential analysis of proteins in grain samples as well as other quantitative surface measurements. Non-kinetic quantitative data for tris-(2,2'-bipyridyl)-ruthenium(II) ion-exchanged into a 13X zeolite are also presented. A calibration curve for the ruthenium chromophore was prepared by cogrinding tris-(2,2'-bipyridyl)-ruthenium(II) dichloride hexahydrate with various amounts of 600 mesh 13X zeolite. Percent relative standard deviations from 1-8% for 0.2 - 2.7 wt% ruthenium salt concentrations were obtained. In addition, a quantitative calibration curve for samarium oxide was prepared by simply mixing controlled particle size distributions of samarium oxide and barium sulfate.
Surfaces play a crucial role in a variety of diverse chemical processes. Many areas of research in catalysis, energy development, semiconductor physics, materials science, biology, and medicine require high technology in surface science. The principle advantage of photoacoustic spectroscopy is that it permits the acquisition of optical spectra similar to those from optical transmission spectroscopy on the surface of any type of opaque condensed phase material.
The photoacoustic effect is an energy conversion process transforming light energy into acoustic energy. In the absence of fluorescence and photochemical reactions, the absorption of modulated monochromatic light by a sample manifest itself as a periodic thermal fluctuation at the modulation frequency as a result of nonradiative de-excitation processes within the sample. The resultant heat flow into the surrounding gas creates a periodic pressure change detected by a sensitive microphone in an enclosed cell.
A lockin amplifier is used to enhance the signal-to-noise of the microphone output. The analog output from the lockin amplifier is transferred to the digital domain with a 10 KHz voltage-to-frequency converter. An ADD-8080 microcomputer provides the artificial intelligence for the automated photoacoustic spectrometer. BASIC language programming allows operator control of the experimental instrumental parameters and flexibility in data manipulation and graphical display.
The single beam photoacoustic spectrometer was constructed from a 300W high intensity Eimac xenon lamp, Heath monochromator, and Brookdeal 9505E lockin amplifier. The detector was a one-inch diameter General Radio electret microphone. A silicon photodiode was used as a reference detector for compensation of temporal light intensity changes.
Issue Date:1981
Description:163 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
Other Identifier(s):(UMI)AAI8114392
Date Available in IDEALS:2014-12-13
Date Deposited:1981

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